1. Field
The present application relates generally to the operation and design of a RF front end for use in portable devices, and more particularly, to methods and apparatus for a switchable balun for combined BLUETOOTH® and WLAN operation.
2. Background
Efficient signal transmission and reception is especially important in portable devices due to limits on circuitry size and power constraints. Typically, such devices include a power amplifier that is coupled to a balanced-to-unbalance (balun) transformer that is used to transform balanced signals from the power amplifier (PA) to unbalanced signals that are coupled to an antenna for transmission.
Advances in communication systems have resulted in the development of various types of wireless networks that may be accessed by a portable device. For example, a wireless local area network (WLAN) may be accessed by a portable device to allow communication with other devices over a localized area such as an office complex or a home. Alternatively, a BLUETOOTH® (BT) network may be accessed by a portable device to allow the device to control printers, hard drives or other types of devices over a relatively short distance. Thus, as a portable device moves from one region to another, one or more wireless networks may become accessible to the device.
Typically, a device includes dedicated circuitry to allow communications with a particular type of wireless network. Thus, devices offering support for both BT and WLAN networks include separate circuitry to accommodate the different power requirements. For example, devices that are operable to communicate over both BT and WLAN networks include multiple transmitter circuits each comprising a separate PA, balun, and support circuitry. Unfortunately, having multiple transmit circuits to support multiple network connections increases costs and circuit board space requirements.
Therefore, it would be desirable to have a transmitter circuit that can be optimally tuned to communicate with both BT and WLAN networks thereby reducing the component count, costs, and/or circuit size when compared to conventional circuits.